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前言
在微信小程序开发中,经常需要实现分享海报功能,通常包含动态二维码。本文将详细介绍如何在小程序中生成带有二维码的海报,并实现保存到手机相册的功能。
实现原理
整个功能的实现主要包含以下几个步骤:
- 生成二维码
- 绘制海报背景
- 将二维码绘制到海报上
- 将画布导出为图片
- 保存图片到相册
核心代码实现
1. 二维码生成工具类
首先,我们需要一个二维码生成的工具类。这里使用优化后的 QRCode 工具:
qrcode.js：绘制二维码
// qrcode.js 绘制二维码
!(function () {
// alignment pattern
var adelta = [
0, 11, 15, 19, 23, 27, 31, 16, 18, 20, 22, 24, 26, 28, 20, 22, 24, 24, 26, 28, 28, 22, 24, 24, 26, 26, 28, 28, 24, 24, 26, 26,
26, 28, 28, 24, 26, 26, 26, 28, 28
];
// version block
var vpat = [
0xc94, 0x5bc, 0xa99, 0x4d3, 0xbf6, 0x762, 0x847, 0x60d, 0x928, 0xb78, 0x45d, 0xa17, 0x532, 0x9a6, 0x683, 0x8c9, 0x7ec, 0xec4,
0x1e1, 0xfab, 0x08e, 0xc1a, 0x33f, 0xd75, 0x250, 0x9d5, 0x6f0, 0x8ba, 0x79f, 0xb0b, 0x42e, 0xa64, 0x541, 0xc69
];
// final format bits with mask: level << 3 | mask
var fmtword = [
0x77c4,
0x72f3,
0x7daa,
0x789d,
0x662f,
0x6318,
0x6c41,
0x6976, //L
0x5412,
0x5125,
0x5e7c,
0x5b4b,
0x45f9,
0x40ce,
0x4f97,
0x4aa0, //M
0x355f,
0x3068,
0x3f31,
0x3a06,
0x24b4,
0x2183,
0x2eda,
0x2bed, //Q
0x1689,
0x13be,
0x1ce7,
0x19d0,
0x0762,
0x0255,
0x0d0c,
0x083b //H
];
// 4 per version: number of blocks 1,2; data width; ecc width
var eccblocks = [
1, 0, 19, 7, 1, 0, 16, 10, 1, 0, 13, 13, 1, 0, 9, 17, 1, 0, 34, 10, 1, 0, 28, 16, 1, 0, 22, 22, 1, 0, 16, 28, 1, 0, 55, 15, 1,
0, 44, 26, 2, 0, 17, 18, 2, 0, 13, 22, 1, 0, 80, 20, 2, 0, 32, 18, 2, 0, 24, 26, 4, 0, 9, 16, 1, 0, 108, 26, 2, 0, 43, 24, 2,
2, 15, 18, 2, 2, 11, 22, 2, 0, 68, 18, 4, 0, 27, 16, 4, 0, 19, 24, 4, 0, 15, 28, 2, 0, 78, 20, 4, 0, 31, 18, 2, 4, 14, 18, 4,
1, 13, 26, 2, 0, 97, 24, 2, 2, 38, 22, 4, 2, 18, 22, 4, 2, 14, 26, 2, 0, 116, 30, 3, 2, 36, 22, 4, 4, 16, 20, 4, 4, 12, 24, 2,
2, 68, 18, 4, 1, 43, 26, 6, 2, 19, 24, 6, 2, 15, 28, 4, 0, 81, 20, 1, 4, 50, 30, 4, 4, 22, 28, 3, 8, 12, 24, 2, 2, 92, 24, 6,
2, 36, 22, 4, 6, 20, 26, 7, 4, 14, 28, 4, 0, 107, 26, 8, 1, 37, 22, 8, 4, 20, 24, 12, 4, 11, 22, 3, 1, 115, 30, 4, 5, 40, 24,
11, 5, 16, 20, 11, 5, 12, 24, 5, 1, 87, 22, 5, 5, 41, 24, 5, 7, 24, 30, 11, 7, 12, 24, 5, 1, 98, 24, 7, 3, 45, 28, 15, 2, 19,
24, 3, 13, 15, 30, 1, 5, 107, 28, 10, 1, 46, 28, 1, 15, 22, 28, 2, 17, 14, 28, 5, 1, 120, 30, 9, 4, 43, 26, 17, 1, 22, 28, 2,
19, 14, 28, 3, 4, 113, 28, 3, 11, 44, 26, 17, 4, 21, 26, 9, 16, 13, 26, 3, 5, 107, 28, 3, 13, 41, 26, 15, 5, 24, 30, 15, 10,
15, 28, 4, 4, 116, 28, 17, 0, 42, 26, 17, 6, 22, 28, 19, 6, 16, 30, 2, 7, 111, 28, 17, 0, 46, 28, 7, 16, 24, 30, 34, 0, 13,
24, 4, 5, 121, 30, 4, 14, 47, 28, 11, 14, 24, 30, 16, 14, 15, 30, 6, 4, 117, 30, 6, 14, 45, 28, 11, 16, 24, 30, 30, 2, 16, 30,
8, 4, 106, 26, 8, 13, 47, 28, 7, 22, 24, 30, 22, 13, 15, 30, 10, 2, 114, 28, 19, 4, 46, 28, 28, 6, 22, 28, 33, 4, 16, 30, 8,
4, 122, 30, 22, 3, 45, 28, 8, 26, 23, 30, 12, 28, 15, 30, 3, 10, 117, 30, 3, 23, 45, 28, 4, 31, 24, 30, 11, 31, 15, 30, 7, 7,
116, 30, 21, 7, 45, 28, 1, 37, 23, 30, 19, 26, 15, 30, 5, 10, 115, 30, 19, 10, 47, 28, 15, 25, 24, 30, 23, 25, 15, 30, 13, 3,
115, 30, 2, 29, 46, 28, 42, 1, 24, 30, 23, 28, 15, 30, 17, 0, 115, 30, 10, 23, 46, 28, 10, 35, 24, 30, 19, 35, 15, 30, 17, 1,
115, 30, 14, 21, 46, 28, 29, 19, 24, 30, 11, 46, 15, 30, 13, 6, 115, 30, 14, 23, 46, 28, 44, 7, 24, 30, 59, 1, 16, 30, 12, 7,
121, 30, 12, 26, 47, 28, 39, 14, 24, 30, 22, 41, 15, 30, 6, 14, 121, 30, 6, 34, 47, 28, 46, 10, 24, 30, 2, 64, 15, 30, 17, 4,
122, 30, 29, 14, 46, 28, 49, 10, 24, 30, 24, 46, 15, 30, 4, 18, 122, 30, 13, 32, 46, 28, 48, 14, 24, 30, 42, 32, 15, 30, 20,
4, 117, 30, 40, 7, 47, 28, 43, 22, 24, 30, 10, 67, 15, 30, 19, 6, 118, 30, 18, 31, 47, 28, 34, 34, 24, 30, 20, 61, 15, 30
];
// Galois field log table
var glog = [
0xff, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b, 0x04, 0x64, 0xe0, 0x0e, 0x34,
0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71, 0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21, 0x35, 0x93,
0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45, 0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9, 0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72,
0xa6, 0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd, 0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88, 0x36, 0xd0, 0x94, 0xce,
0x8f, 0x96, 0xdb, 0xbd, 0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40, 0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e, 0x6b,
0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d, 0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b, 0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3,
0xa7, 0x57, 0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d, 0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18, 0xe3, 0xa5, 0x99,
0x77, 0x26, 0xb8, 0xb4, 0x7c, 0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e, 0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd,
0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61, 0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e, 0x84, 0x3c, 0x39, 0x53, 0x47,
0x6d, 0x41, 0xa2, 0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76, 0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6, 0x6c, 0xa1,
0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa, 0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a, 0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0,
0x51, 0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7, 0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8, 0x74, 0xd6, 0xf4, 0xea,
0xa8, 0x50, 0x58, 0xaf
];
// Galios field exponent table
var gexp = [
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26, 0x4c, 0x98, 0x2d, 0x5a, 0xb4,
0x75, 0xea, 0xc9, 0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0, 0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35, 0x6a, 0xd4,
0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23, 0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0, 0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde,
0xa1, 0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc, 0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0, 0xfd, 0xe7, 0xd3, 0xbb,
0x6b, 0xd6, 0xb1, 0x7f, 0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2, 0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88, 0x0d,
0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce, 0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93, 0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33,
0x66, 0xcc, 0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9, 0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54, 0xa8, 0x4d, 0x9a,
0x29, 0x52, 0xa4, 0x55, 0xaa, 0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73, 0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e,
0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff, 0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4, 0x95, 0x37, 0x6e, 0xdc, 0xa5,
0x57, 0xae, 0x41, 0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6, 0x51, 0xa2,
0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef, 0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09, 0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4,
0xf5, 0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16, 0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83, 0x1b, 0x36, 0x6c, 0xd8,
0xad, 0x47, 0x8e, 0x00
];
// Working buffers:
// data input and ecc append, image working buffer, fixed part of image, run lengths for badness
var strinbuf = [],
eccbuf = [],
qrframe = [],
framask = [],
rlens = [];
// Control values - width is based on version, last 4 are from table.
var version, width, neccblk1, neccblk2, datablkw, eccblkwid;
var ecclevel = 2;
// set bit to indicate cell in qrframe is immutable. symmetric around diagonal
function setmask(x, y) {
var bt;
if (x > y) {
bt = x;
x = y;
y = bt;
}
// y*y = 1+3+5...
bt = y;
bt *= y;
bt += y;
bt >>= 1;
bt += x;
framask[bt] = 1;
}
// enter alignment pattern - black to qrframe, white to mask (later black frame merged to mask)
function putalign(x, y) {
var j;
qrframe[x + width * y] = 1;
for (j = -2; j < 2; j++) {
qrframe[x + j + width * (y - 2)] = 1;
qrframe[x - 2 + width * (y + j + 1)] = 1;
qrframe[x + 2 + width * (y + j)] = 1;
qrframe[x + j + 1 + width * (y + 2)] = 1;
}
for (j = 0; j < 2; j&#